AM33: enable inc4 for data registers...

[Alexandre Oliva]

... and fix the condition-codes of inc4 for address registers.
It causes negligible (IMO :-) increase in code size:

^ mn10300-elf/am33/libiberty/libiberty.a 28016 28025
^ mn10300-elf/am33/libio/libio.a 23731 23733
^ mn10300-elf/am33/libio/libiostream.a 63981 63987
^ mn10300-elf/am33/libstdc++/libstdc++.a 69843 69850
^ mn10300-elf/am33/newlib/libc.a 47680 47683
^ mn10300-elf/am33/newlib/libc/libc.a 46233 46236
^ mn10300-elf/am33/newlib/libc/stdlib/lib.a 20370 20373
^ mn10300-elf/am33/newlib/libg.a 47680 47683
^ mn10300-elf/am33/newlib/libm.a 96509 96510
^ mn10300-elf/am33/newlib/libm/libm.a 96509 96510
^ mn10300-elf/am33/newlib/libm/math/lib.a 88179 88180

Ok to install?  (this patch assumes am33-gcc-add-sp.patch is already
installed, but it does not depend on it, i.e., there is an overlap
that requires one patch to be tweaked to be installed without the
other.)